In recent years, correlation between the number of circulating tumor cells (CTCs) in peripheral blood and survival in metastatic cancer patients has been reported. These reports demonstrate that the number of CTCs can provide an early and reproducible indication of disease progression and treatment efficacy, and establish CTCs as an emerging and important marker of disease status. The detection of CTCs thus may represent an early indication of micro-metastasis caused by the shedding of tumor cells from aggressive tumors into blood. The ability to isolate CTCs and subsequently profile the biochemical changes that have occurred in these cells will greatly enhance our understanding both of cancer metastases and in assessing the metastatic risks of cancer patients. It is, however, difficult to detect and study CTCs. The principal difficulty originates from the rarity of CTCs, especially in peripheral blood where they are the most accessible from a clinical perspective. To address this challenge, we propose to develop a sensitive technique for the isolation of CTCs from blood. Our approach is based on aliquoting blood into nanoliter-volume droplets, high-sensitivity and high-speed optical detection of a CTC within the nanoliter-volume droplet in a flow-through format, sorting of the droplet that contains the CTC, and isolation of the CTCs contained within the sorted droplets. Our specific aims are: (1) Develop a microfluidic device for aliquoting blood into nanoliter-volume droplets and an optical system for the high sensitivity flow-through detection of a fluorescently labeled CTC contained in the nanoliter aliquot of blood. To increase the sensitivity and throughput of our method, we will also develop and employ conjugated-polymer dots (CPdots)-tagged antibodies as highly fluorescent labels of CTCs. CPdots are orders of magnitude more fluorescent than dyes or quantum dots, thereby allowing us to detect CTCs with a high signal-to-noise in fast flow. (2) Develop an appropriate microfluidic-based sorting technique for sorting the droplet containing the detected CTC. (3) Develop a method to remove CTCs from the sorted droplets and from other blood cells present in the droplets. PUBLIC HEALTH RELEVANCE: Circulating tumor cells have been advocated as a marker of cancer prognosis because these cells are the ones that get lodged in organs to give rise to vascularized macrometastases. Here, we propose to develop a highly sensitive technique for the detection and isolation of circulating cancer cells from whole blood. The availability of this tool will allow for a better understanding of the makeup and physiology of these cells, which in turn will facilitate the development of more accurate prognostic markers as well as more effective therapies to eradicate these cancer cells.